Plant Disease magazine, April 2005 issue, Volume 89, Number 3
Selection of articles relevant to seed professionals

Subscribers to Plant Disease magazine can follow the links to the full articles (PDF format)

Sensitivity of Venturia inaequalis Populations to Anilinopyrimidine Fungicides and Their Contribution to Scab Management in New York.
Wolfram Köller, W. F. Wilcox, and D. M. Parker. Pages 357-365. DOI: 10.1094/PD-89-0357.

Characterization of California Isolates of Fusarium oxysporum f. sp. vasinfectum.
Y. Kim, R. B. Hutmacher, and R. M. Davis. Pages 366-372. DOI: 10.1094/PD-89-0366.  

Interpretive Summary
Fusarium wilt of cotton is a widespread disease in the United States and most cotton-growing areas of the world. Until a few years ago, the disease caused mild symptoms on widely grown cotton cultivars. Recently, two developments have raised concerns about Fusarium wilt of cotton in the San Joaquin Valley of California. The first was the emergence of extremely virulent strains of the causal agent, Fusarium oxysporum f. sp. vasinfectum, in Australia. When the California dairy industry began importing hundreds of thousands of metric tons of Australian cotton seed for feed in the late 1990s, cotton growers worried about the possible introduction of these strains into local fields. The second concern was the alarming occurrence of serious economic losses to Fusarium wilt in some Pima cotton fields in California. Because of these issues, an investigation was needed to determine the diversity and locality of California strains. Although eight races of F. oxysporum f. sp. vasinfectum have been described throughout the world, only race 1 and race 2 were known to occur in the United States. In this study, we identified the existence of four races of the pathogen in California. One of the races, race 4, was responsible for the extensive crop losses in the infested Pima fields. Australian isolates were not found in California. This is the first report of the occurrence of races 3, 4, and 8 in California.

Greenhouse Evaluation of Binucleate Rhizoctonia for Control of R. solani in Soybean.
F. U. Khan, B. D. Nelson, and T. C. Helms. Pages 373-379. DOI: 10.1094/PD-89-0373.  

Interpretive Summary
The fungal pathogen Rhizoctonia solani attacks soybeans and other crops and causes damage to seedlings and adult plants. This pathogen lives in the soil and is difficult to control. One method of controlling the diseases caused by R. solani is to use other microorganisms that interfere with the activity of the pathogen on the roots of the plant. This greenhouse study investigated the use of strains of binucleate Rhizoctonia, another soil fungus that lives on soybean roots, for the control of R. solani. Results showed that binucleate Rhizoctonia can reduce the amount of disease if they grow on the roots prior to the pathogen attacking the plant. Field studies are needed to determine if the binucleate Rhizoctonia have any practical use in reducing diseases in soybean production.

Limited Genetic Diversity in North American Isolates of Phytophthora erythroseptica Pathogenic to Potato Based on RAPD Analysis.
Rick D. Peters, Rod J. Clark, Albert D. Coffin, Antony V. Sturz, David H. Lambert, and Jeff S. Miller. Pages 380-384. DOI: 10.1094/PD-89-0380.

Genetics of Chickpea Resistance to Five Races of Fusarium Wilt and a Concise Set of Race Differentials for Fusarium oxysporum f. sp. ciceris.
Kamal Dev Sharma, Weidong Chen, and Fred J. Muehlbauer. Pages 385-390. DOI: 10.1094/PD-89-0385.  

Interpretive Summary
Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris is an important disease in many chickpea production regions. There are at least eight different races of the pathogen. Resistance to the races of Fusarium wilt is generally conditioned by major resistance genes. The genetics of resistance to race 5 in chickpea line WR-315 is not known, and the genetics of resistance to race 2 is controversial. This study using 100 F7 recombinant inbred lines derived from a cross between WR-315 and C-104 showed that resistance to race 5 in WR-315 is conditioned by one gene. It also showed that resistance to race 2 in WR-315 is conditioned by a single recessive gene. Knowing the number of genes involved in resistance is important in devising strategies to move the resistance genes to elite breeding lines and cultivars. We also observed a phenomenon termed slow wilting, which is different from previously reported late wilting in three aspects: latent period, disease progress rate, and final disease incidence. Identification of races is usually through using chickpea differentials. Previously reported differentials are imprecise in distinguishing some races, particularly in separating between races 2 and 3. We identified a recombinant inbred line that can be used to unambiguously separate races 2 and 3. After evaluating previously used differentials, we developed a concise differential set of eight chickpea lines that will offer important improvements over previous differential sets and will provide more precise and unambiguous identification of the races.

Seasonal Progression and Agronomic Impact of Tobacco streak virus on Soybean in Wisconsin.
P. F. Rabedeaux, J. M. Gaska, N. C. Kurtzweil, and C. R. Grau. Pages 391-396. DOI: 10.1094/PD-89-0391.

Effect of Temperature on Apothecial Longevity and Ascospore Discharge by Apothecia of Monilinia vaccinii-corymbosi.
Phillip S. Wharton and Annemiek C. Schilder. Pages 397-403. DOI: 10.1094/PD-89-0397.

Evaluation of Components of Fusarium Head Blight Resistance in Soft Red Winter Wheat Germ Plasm Using a Detached Leaf Assay.
R. A. Browne, J. P. Murphy, B. M. Cooke, D. Devaney, E. J. Walsh, C. A. Griffey, J. A. Hancock, S. A. Harrison, P. Hart, F. L. Kolb, A. L. McKendry, E. A. Milus, C. Sneller, and D. A. Van Sanford. Pages 404-411. DOI: 10.1094/PD-89-0404.

Winter Survival of the Perennial Ryegrass Pathogen Magnaporthe oryzae in North Central Indiana.
Philip F. Harmon and Richard Latin. Pages 412-418. DOI: 10.1094/PD-89-0412

DISEASE NOTES (excerpts, relevant to seed professionals)
Subscribers to Plant Disease magazine can follow the links to the full reports

First Report of an Alternaria Leaf Spot Caused by Alternaria brassicae on Crambe abyssinicia in Australia. M. P. You, P. Simoneau, A. Dongo, M. J. Barbetti, Hua Li, and K. Sivasithamparam. Page 430. DOI: 10.1094/PD-89-0430A.

First Report of Turnip mosaic virus in Rhubarb in Alaska. N. L. Robertson and D. C. Ianson. Page 430. DOI: 10.1094/PD-89-0430B.

Shoot Blight of Forsythia × intermedia in Virginia Nurseries Caused by Phytophthora nicotianae. C. X. Hong, P. A. Richardson, and P. Kong. Page 430. DOI: 10.1094/PD-89-0430C.

Powdery Mildew Caused by Leveillula taurica on Glossy Leaf Genotypes of Onion in Idaho. S. K. Mohan and N. D. Molenaar. Page 431. DOI: 10.1094/PD-89-0431C.

First Report of Plectosporium Blight on Pumpkin and Squash Caused by Plectosporium tabacinum in New York. P. Jimenez and T. A. Zitter. Page 432. DOI: 10.1094/PD-89-0432A.

Occurrence of Fusarium Wilt on Canola Caused by Fusarium oxysporum f. sp. conglutinans in Argentina. S. A. Gaetán. Page 432. DOI: 10.1094/PD-89-0432C.

First Report of Pyricularia grisea Causing Gray Leaf Spot on Kikuyugrass (Pennisetum clandestinum) in the United States. F. P. Wong, W. Gelernter, and L. Stowell. Page 433. DOI: 10.1094/PD-89-0433C.

Late Blight Caused by Phytophthora infestans on Solanum sarrachoides in Northeastern Maine. K. L. Deahl, R. Jones, L. A. Wanner, and A. Plant. Page 435. DOI: 10.1094/PD-89-0435A.

First Outbreak of Blackleg Caused by Phoma lingam in Commercial Canola Fields in Argentina. S. A. Gaetán. Page 435. DOI: 10.1094/PD-89-0435B.